A lateral double diffused metal-oxide semiconductor (LDMOS), as a majority carrier device, may serve as a power device capable of fast switching response and high input impedance. Since the LDMOS may be used as a switching device, it requires a short channel length to drive a high current. Also, to withstand high voltage, the LDMOS needs to be designed with a high doping density in the P-type body so that punch-through breakdown is not caused by a reverse bias.
A channel may be produced by implanting boron into a P-type body region, implanting arsenic into a substrate using a single mask, and then performing a thermal treatment. Here, the length of the channel is determined by the difference in diffusion rates between boron and arsenic, which in turn is dependent on temperature and the time of the thermal treatment. Punch-through breakdown can be avoided by adjusting the implantation concentration at the P-type body, even though the channel is very short.
A doping profile in the channel region is not uniform since the doping concentration is high in a source region, while the doping concentration is low at an end of the channel. The channel length may not be varied because the channel doping profile is not uniform. Therefore, the size of the channel may be adjusted only by controlling a gate width.